Electroplating



2,839,456 Patented June 17, 1958 ELECTROPLATIN G Donald Gardner Foulke,Watchung, and Otto Kardos,

Red Bank, N. J., assignors to Hanson-Van Winkle- Munning Company, acorporation .of New Jersey No Drawing. Application November 16, 1956Serial No. 622,529

6 Claims. (Cl. 204-49) This invention relates to electroplating and,more particularly, to electrodepositing nickel from an acidic nickelplating bath. The invention is based on our discovery that 2-(4-pyridyl)ethyl sulfonic acid, and certain of its salts, when incorporated in anickel electroplating bath in combination with various sulfo-oxygeucompounds, is capable of producing excellent bright ductile nickelelectrodeposits over a wide current density range. We have found that inall instances the combined use of 2-(4-pyridyl) ethyl sulfonic acid andthe sulfo-oxygen compound exerts a synergistic effect on the brighteningcapacity of the bath as compared with the use of either compound alone.

A preferred process according to this invention for producing brightnickel deposits comprises electrodepositing nickel from an aqueousacidic solution of at least one nickel salt, in which there is dissolvedfrom about 0.1 to about 10 grams per liter of 2-(4-pyridyl) ethylsulfonic acid or an alkali metal, magnesium, ammonium, or nickel saltthereof, together with from about A to about 80 grams per liter of awater-soluble sulfo-oxygen compound of the group consisting ofmononuclear and binuclear aromatic sulfonic acids, mononuclear aromaticsulfinic acids, the alkali metal, magnesium, ammonium,

and nickel salts of said acids, and mononuclear aromatic sulfonamidesand sulfonimides.

The compounds listed in Table I are examples of sulfo-oxygen compoundswhich, when used in combination with 2-(4-pyridyl) ethyl sulfonic acidand its abovementioned salts, promote the formation of brilliant andductile nickel deposits. These sulfo-oxygen compounds may be used over awide range of concentrations 4 to 80 grams per liter), but preferablyare used in an amount in the range from about 1 to 20 grams per liter.

TABLE I Organic sulfa-oxygen compounds (1) Unsaturated aliphaticsulfonic acids, and alkali metal, ammonium, magnesium, and nickel saltsthereof:

Sodium vinyl sulfonate, H C=CHSO Na Sodium allyl sulfonate, H C=CHCH SONa (2) Mononuclear aromatic sulfonic acids, and alkali metal, ammonium,magnesium, and nickel salts thereof:

Benzene monosulfonic acid, C H SO H Sodium benzene monosulfonate, C H SONa Nickel benzene mouosulfonate, (C H SO Ni Sodium p-toluenemonosulfonate, CH C H SO Na p-Chlorobenzene sulfonic acid, ClC H SO I-ISodium p-chlorobenzene sulfonate, ClC H,SO Na Sodium p-bromobenzenesulfonate, BrC H SO Na 1,2-dichlorobenzene sulfonic acid, Cl C H SO H1,2- or 2,5-dichlorobenzene sulfonates, sodium salt,

m-Benzene disulfonic acid, C H (SO H) Sodium m-benzene disulfonate, C H(SO Na) 2 Nickel m-benzene disulfonate, C H (SO Ni o-Sulfobenzoic acidmonoammonium salt,

l-amino-2,5-benzene disulfonic acid, H NC H (SO H) o-Aminobenzenesulfonic acid, H NC H SO H (3) Mononuclear aromatic sulfinic acids, andalkali metal, ammonium, magnesium, and nickel salts thereof:

Sodium benzene sulfinate, C H SO Na Sodium p-toluene sulfinate, CI-I C HSO Na.

(4) ltlononuclear aromatic sulfonamides and sulfonimides Benzenesulfonamide, C H SO NH p-Toluene sulfonamide, CH C H SO NHo-Sulfobenzoic imide CaHiC ONHSOZ Benzyl sulfonamide, C H CH SO NHBenzene sulfhydroxamic acid, C H SO NHOH N,N-dimethylp-toluenesulfonamide,

CH C H SO N(CH N,N-dicarboxyethyl benzene sulfonamide,

C H SO N(C H COOH) (5)Binuclear aromatic sulfonic acids, and alkalimetal, ammonium, magnesium, and nickel salts thereof:

(6) Heterocyclic sulfonic acids, and alkali metal, ammonium, magnesium,andlnickel salts thereof:

Thiophene sulfonic acid, C H S SO H Sodium thiophene sulfonate, C H S-SONa ,For the most part, only free sulfonic acids are listed in Table I.However, the alkali metal, ammonium, magnesium, and nickel salts are inall cases thetfull equivalent of the acids, and may be used in theirplace in carrying out the process of this invention. i

Brightener additions according to this invention have, of course, beenused successfully in the standard Watts nickel electroplating bath.However, these brightener additions are also efifective in all otheracid. nickel electroplating baths, and consequently the invention isapplicable to any nickel electrodeposition from an aqueous acidicsolution of one or more nickel salts.

To illustrate the applicability of using 2-(4-pyridyl) ethyl sulfonicacid in diiferent nickel electroplating baths under a variety ofconditions, Table II lists the basic compositions of several types ofplating baths which were employed in carrying out the examples of theinvention that are set forth below.

TABLE II Bath concentrations in grams per liter Bath A Bath 0 Bath 0Nickel sulfate l 300 Nickel chloride. Nickel sulfamata Nickel fluoborateBoric acid In each of the following examples of the invention, theelectrodeposit was formed in a Hull test cell on brass cathodes so thatthe effect of a wide range of current densities could be observed. ThepH of the bath was adjusted to about 3.5 to 4 inxeach case, and theelectrodeposit was formed at a temperature of 50 C.

EXAMPLE I To the'Watts bath (bath A) described in Table II were added 2grams .per liter'of sodium 2-(4-pyridy'l) ethyl sulfonate. Afteradjusting the voltage through the Hull test cell to give a total currentof two amperes, the test panel received a nickel electroplate which wasonly fairly bright over the lower 70 percent of the entire currentdensity range.

In a comparative operation, 0.3 gram per liter of so dium 2-(4-pyridyl)ethyl sulfonate and 16 grams per liter of sodium 1,3,6-naphthalenetriisulfonate were added to a freshly prepared plating solution havingthe composition of bath A. Again at a total current of two amperes, thenickel electroplate formed on the panel was very bright, over the entirecurrent density range, and distinctly brighter than the control panelsplated from a Watts bath containing 16 grams per liter of thetrisulfonate alone. Increasing the concentration of sodium2-(4-.pyridyl) ethyl sulfonate to 0.6 and 0.8 gram per liter in a bathalso containing the naphthalene trisulfonate substantially increased thebrightness of the electroplate.

EXAMPLE II As a general rule, the synergistic effect of 2-(4-pyridyl)ethyl sulfonic acid on the brightening capacity of sulfooxygen compoundsis most pronounced at high current densities. The test panel of a Hullcell received a nickel electrodeposit from bath A which contained 4grams per liter of sodium benzene sulfonate. Although the plated panelwas fairly bright in the central and lower current density ranges, itwas streaked and matted at the upper current density range. By adding 1gram per liter of sodium 2-(4-pyridyl) ethyl sulfonate to theelectroplating solution, the nickel dcposit became very bright oversubstantially the entire current density range. Increasing the sodiumbenzene sul'fonate to 8 grams per liter had no eitect on the brightness,but improved the ductility of the electrodeposit.

EXAMPLE III Brilliant nickel deposits are formed when the 1pyridyl ethylsulfonic acid is used in conjunction with aromatic sulfonamides orsulfonimides. Table III sets forth in detail the results achieved whennickel is electrodeposited Sulfo-Oxygen Compound (2 grams/liter) Sodium2- i-pyridyl) ethyl Results sulionate (grams/liter) Very bright.Brilliant and ductile.

Do. Very bright with no brittleness.

o-Sulfobenzoic imide Benzene sulfonamidc Benzyl sulfonamide EXAMPLE IVTo a sulfamate nickel plating bath (bath B), which had been properlypurified, was added 1.6 grams per liter of sodium Z M-pyridyl) ethylsulfonate, and nickel electrodeposited on a Hull test panel. The depositwas brittle and moderately bright over only the lower 60 percent of thetest panel. Increasing the sodium 2-(4- 'pyridyl) ethyl sulfonate to 3.2grams per liter did not increase the brightness nor extend the range.Upon the addition of 15 grams per liter of sodium 1,3,6-naphthalenetrisuiionate to this bath, the brightening range was markedly extended,and the brittleness of the deposit reduced.

When 15 grams per liter of sodium 1,3,6-naphthalenc trisulfonate wereadded to a plating solution of the same basic composition but notcontaining the ethyl sulfonate, the deposit was only semi-bright over awide current density range with a strong haze at the middle and lowcurrent densities. Addition of 0.4 to 0.8 gram per liter of2-(4-pyridyl) ethyl sulfonic acid to this bath strongly reduced thishaze.

EXAMPLE V Using a nickel fiuoborate bath (bath C) which had eenpreviously purified, the electrodeposition of nickel from such bath at50 C. and at a pH of about 3.0 in 8. Hull cell was scarcely affected byadding 3.2 grams per liter of Z-( i-pyridyl) ethyl sulfonic acid to thebath. The useof 15 grams per liter of sodium 1,3,6-naphtha1enetrisultonate alone in the same iluoborate bath produced only a hazysemi-brightness. When, however, both 15 grams per liter of sodium1,3,6-naphthalene trisulfonate and 1.6 grams per liter of sodium2-(4-pyridyl) ethyl sulfonate Were combined in a freshly prepared nickelfluoborate bath, the resulting nickel deposits were bright over a Widecurrent density range.

Although the examples have, for the most part, illustrated the use ofsodium 2-(4-pyridyl) ethyl sulfonate, or the free acid, the remainingalkali metal, ammonium,

' magnesium and nickel salts of this acid are fully equivalent, and maybe used to carry out the process of this invention.

The synergistic effect of 2-(4-pyridyl) ethyl sulfonic acid, or itsaforementioned salts, may be obtained by using concentrations as low as0.1 gram per liter in the plating bath. Although concentrations inexcess of 10 grams per liter may be employed, there is no particularadvantage to be gained from the higher concentrations.

We claim:

1. The process for producing bright nickel deposits which compriseselectrodepositing nickel from an aqueous acidic solution of at least onenickel salt in which there is dissolved from about 0.1 to about 10 gramsper liter of a heterocyclic organic compound of the group consisting of2-(4-pyridyl) ethyl sulfonic acid and the alkali metal, magnesium,ammonium, and nickel salts thereof, and from about A to about 80 gramsper liter of a watersoluble sulfo-oxygcn compound of the groupconsisting of unsaturated aliphatic sulfonic acids, mononuclear andbinuclear aromatic sulfonic acids, mononuclear aromatic sulfinic acids,the alkali metal, magnesium, ammonium, and nickel salts of said acids,and mononuclear aromatic sulfonamides and sulfonimides.

2. The method according to claim 1, in which the concentration of thesulfo-oxygen compound is in the range from i to 20 grams per liter.

3. The process for producting bright nickel deposits which compriseselectrodepositing nickel from an aqueous acidic solution of at least onenickel salt in which there is dissolved from about 0.1 to about 10grains per liter of a heterocyclic organic compound of the groupconsisting of 2-(4-pyridyl) ethyl sulfonic acid and the alkali metal,magnesium, ammonium, and nickel salts thereof} and from about /4 toabout 20 grams per liter of o-sulfobenzoic imide. I

4. An aqueous acidic nickel electroplating bath in which there isdissolved from about 0.1 to about 10 grams per liter of a heterocyclicorganic compound of the group consisting of 2-(4-pyridyl) ethyl sulfonicacid and the alkali metal, magnesium, ammonium, and nickel saltsthereof, and from about to about 80 grams per liter of a Water-solublesulfo-oxygen compound of the group consisting of-unsaturated aliphaticsulfonic acids, mononuclear and binuclear aromatic sulfonic acids,mononuclear aromatic sulfinie acids, the alkali metal, magnesium,ammonium, and nickel salts of said acids, and mononuclear aromaticsulfonarnides and sulfonimides.

5. An aqueous acidic nickel electroplating bath according to claim 4, inWhich the concentration of the sulfo-oxygen compound is in the rangefrom 1 to 20 grams per liter.

6. An aqueous acidic nickel electroplating bath in Which there isdissolved from about 0.1 to about 10 grams per liter of a hetero-cyclicorganic compound of the group consisting of 2-(4-pyridyl) ethyl sulfonicacid and the alkali metal, magnesium, ammonium, and nickel saltsthereof, and from about A to about 20 grams per liter of osulfobenzoicimide.

References Cited in the file of this patent UNITED STATES PATENTS2,513,280 Brown July 4, 1950 2,550,449 Brown Apr. 24, 1951 2,644,788Shenk July 7, 1953 2,647,866 Brown Aug. 4, 1953

1. THE PROCESS FOR PRODUCING BRIGHT NICKEL DEPOSITS WHICH COMPRISESELECTRODEPOSITING NICKEL FROM AN AQUEOUS ACIDIC SOLUTION OF AT LEAST ONENICKEL SALT IN WHICH THERE IS DISSOLVED FROM ABOUT 0.1 TO ABOUT 10 GRAMSPER LITER OF A HETEROCYCLIC ORGANIC COMPOUND OF THE GROUP CONSISTING OF2-(4-PYRIDYL) ETHYL SULFONIC ACID AND THE ALKALI METAL, MAGNESIUM,AMMONIUM, AND NICKEL SALTS THEREOF, AND FROM ABOUT 1/4 TO ABOUT 80 GRAMSPER LITER OF A WATERSOLUBLE SULFO-OXYGEN COMPOUND OF THE GROUPCONSISTING OF UNSATURATED ALIPHATIC SULFONIC ACIDS, MONONUCLEAR ANDBINUCLEAR AROMATIC SULFONIC ACIDS, MONONUCLEAR AROMATIC SULFINIC ACIDS,THE ALKALI METAL, MAGNESIUM, AMMONIUM, AND NICKEL SALTS OF SAID ACIDS,AND MONONUCLEAR AROMATIC SULFONAMIDES AND SULFONIMIDES.